An operation of loading a refrigerant into a refrigerant circuit of an air conditioner is necessary to start a trial run after the air conditioner has been installed. Patent Document 1 discloses a technique for automatically determining when such a refrigerant loading operation is completed. In the air conditioner disclosed in Patent Document 1, a cylinder operation is necessary for the aforementioned loading operation, but an air conditioner is also known in which the cylinder operation is made unnecessary by preparing in advance a refrigerant regulator, which is a tank filled with the refrigerant.
In the conventional heat source unit provided with the refrigerant regulator, the refrigerant located in the refrigerant regulator is loaded into the refrigerant circuit by connecting to the refrigerant regulator an introducing pipe that is branched off from a discharge-side pipe of the compressor and a lead-out pipe connected to a liquid pipe through which passes the liquid refrigerant after condensation. Thus, the high-pressure gaseous refrigerant discharged from the compressor is introduced into the refrigerant regulator through the introducing pipe, and the refrigerant located inside the refrigerant regulator that has been pressurized by this high-pressure gaseous refrigerant is led out to the lead-out pipe and loaded into the refrigerant circuit. However, since the liquid refrigerant inside the liquid pipe is under a high pressure, even if the liquid refrigerant is pressurized by the high-pressure gas refrigerant, the pressure inside the refrigerant regulator can be increased only slightly above the pressure of liquid refrigerant inside the liquid pipe, a long time is required to complete the loading of the refrigerant from the refrigerant regulator into the refrigerant circuit, the refrigerant loading operation becomes the rate-determining operation, and the trial run time is extended.    Patent Document 1: Japanese Patent Application Laid-open No. 2007-198642